The invention relates to an arrangement for generating a speech signal comprising a synthesizing section, based on the linear prediction, principle for producing a discrete signal consisting of a plurality of consecutive sub-signals, each representing a voiced or unvoiced speech segment, and an output section for converting the discrete signal into the speech signal.
The invention also relates to a method of generating a speech signal.
Arrangements of the type defined in the preamble are described in the book by J. D. Markel and A. H. Gray, Jr. entitled: "Linear Prediction of Speech" (Springer-Verlag 1976), chapter 5 of which describes the general structure of a speech synthesizing arrangement based on the linear predictive coding (LPC) principle, while chapter 10 describes the use of LPC techniques in vocoders.
An article by B. S. Atal and S. L. Hanauer entitled: "Speech Analyses and Synthesis by Linear Prediction of the Speech Wave" in The Journal of the Acoustical Society of America, volume 50, no. 2, 1971, pages 637-655 gives a clear description of an LPC speech synthesizing arrangement, which comprises an adaptive discrete filter whose pulse response is periodically changed on the basis of prediction parameters. Therein, a speech signal is produced at the output of the filter when there is applied to the input a pulse signal for voiced signals and a noise signal for unvoiced signals.
However, the speech signals generated by that type of arrangements have, as known, an annoying buzz in voiced portions of the speech signal.
To reduce this buzz in the synthesized speech signal, the literature mentions several possibilities. Inter alia M. R. Sambur et al. propose, in an article in the Journal of the Acoustical Society of America, Volume 63, no. 3, March 1978, pages 918-924 entitled: "On reducing the buzz in LPC synthesis", to use a pulse having a very special shape with rounded edges instead of, as customary, an impulse for exciting the discrete filter. Although this does indeed effect some improvement, applicants have found that this improvement is rather slight and that the speech signal gets a considerable low-pass character.